GLORIA

GEOMAR Library Ocean Research Information Access

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
  • 1
    In: International Journal of Greenhouse Gas Control, Elsevier BV, Vol. 18 ( 2013-10), p. 510-522
    Type of Medium: Online Resource
    ISSN: 1750-5836
    Language: English
    Publisher: Elsevier BV
    Publication Date: 2013
    detail.hit.zdb_id: 2322650-X
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
  • 2
    In: Geochemical Transactions, Springer Science and Business Media LLC, Vol. 12, No. 1 ( 2011-12)
    Type of Medium: Online Resource
    ISSN: 1467-4866
    Language: English
    Publisher: Springer Science and Business Media LLC
    Publication Date: 2011
    detail.hit.zdb_id: 2033931-8
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
  • 3
    In: GEOPHYSICS, Society of Exploration Geophysicists, Vol. 82, No. 2 ( 2017-03-01), p. M19-M36
    Abstract: Reservoir core measurements can help guide seismic monitoring of fluid-induced pressure variations in tight fractured reservoirs, including those targeted for supercritical [Formula: see text] injection. We have developed the first seismic-frequency “room-dry” measurements of fracture-specific shear stiffness, using artificially fractured standard granite samples with different degrees of mating, a well-mated tensile fracture from a dolomite reservoir core, as well as simple roughened polymethyl methacrylate (PMMA) surfaces. We have adapted a low-frequency (0.01–100 Hz) shear modulus and attenuation apparatus to explore the seismic signature of fractures and understand the mechanics of asperity contacts under a range of normal stress conditions. Our instrument is unique in its ability to measure at low-normal stresses (0.5–20 MPa), simulating “open” fractures in shallow or high-fluid-pressure reservoirs. The accuracy of our instrument is demonstrated by calibration and comparison with ultrasonic measurements and low-frequency direct shear measurements of intact samples from the literature. Pressure-sensitive film was used to measure real contact area of the fracture surfaces. The fractured shear modulus for most of the samples shows an exponential dependence on the real contact area. A simple numerical model, with one bonded circular asperity, predicts this behavior and matches the data for the simple PMMA surfaces. The rock surfaces reach their intact moduli at lower contact area than the model predicts, likely due to more complex geometry. Finally, we apply our results to a linear-slip interface model to estimate reflection coefficients and calculate S-wave time delays due to the lower-wave velocities through the fractured zone. We find that cross-well surveys could detect even well-mated hard-rock fractures, assuming the availability of high-repeatability acquisition systems.
    Type of Medium: Online Resource
    ISSN: 0016-8033 , 1942-2156
    RVK:
    Language: English
    Publisher: Society of Exploration Geophysicists
    Publication Date: 2017
    detail.hit.zdb_id: 2033021-2
    detail.hit.zdb_id: 2184-2
    SSG: 16,13
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
  • 4
    Online Resource
    Online Resource
    Society of Exploration Geophysicists ; 2014
    In:  GEOPHYSICS Vol. 79, No. 6 ( 2014-11-01), p. EN107-EN124
    In: GEOPHYSICS, Society of Exploration Geophysicists, Vol. 79, No. 6 ( 2014-11-01), p. EN107-EN124
    Abstract: Surface waves are advantageous for mapping seismic structures of permafrost, in which irregular velocity gradients are common and thus the effectiveness of refraction methods are limited. Nevertheless, the complex velocity structures that are common in permafrost environments often yield unusual dispersion spectra, in which higher-order and leaky modes are dominant. Such unusual dispersion spectra were prevalent in the multichannel surface-wave data acquired from our permafrost study site at Barrow, Alaska. Owing to the difficulties in picking and identifying dispersion curves from these dispersion spectra, conventional surface-wave inversion methods become problematic to apply. To overcome these difficulties, we adopted a full-wavefield method to invert for velocity models that can best fit the dispersion spectra instead of the dispersion curves. The inferred velocity models were consistent with collocated electric resistivity results and with subsequent confirmation cores, which indicated the reliability of the recovered seismic structures. The results revealed embedded low-velocity zones underlying the ice-rich permafrost at our study site — an unexpected feature considering the low ground temperatures of [Formula: see text] to [Formula: see text] . The low velocities in these zones ([Formula: see text] lower than the overlying ice-rich permafrost) were most likely caused by saline pore-waters that prevent the ground from freezing, and the resultant velocity structures are vivid examples of complex subsurface properties in permafrost terrain. We determined that full-wavefield inversion of surface waves, although carrying higher computational costs than conventional methods, can be an effective tool for delineating the seismic structures of permafrost.
    Type of Medium: Online Resource
    ISSN: 0016-8033 , 1942-2156
    RVK:
    Language: English
    Publisher: Society of Exploration Geophysicists
    Publication Date: 2014
    detail.hit.zdb_id: 2033021-2
    detail.hit.zdb_id: 2184-2
    SSG: 16,13
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
  • 5
    Online Resource
    Online Resource
    American Association for the Advancement of Science (AAAS) ; 2019
    In:  Science Vol. 366, No. 6469 ( 2019-11-29), p. 1103-1107
    In: Science, American Association for the Advancement of Science (AAAS), Vol. 366, No. 6469 ( 2019-11-29), p. 1103-1107
    Abstract: Distributed fiber-optic sensing technology coupled to existing subsea cables (dark fiber) allows observation of ocean and solid earth phenomena. We used an optical fiber from the cable supporting the Monterey Accelerated Research System during a 4-day maintenance period with a distributed acoustic sensing (DAS) instrument operating onshore, creating a ~10,000-component, 20-kilometer-long seismic array. Recordings of a minor earthquake wavefield identified multiple submarine fault zones. Ambient noise was dominated by shoaling ocean surface waves but also contained observations of in situ secondary microseism generation, post–low-tide bores, storm-induced sediment transport, infragravity waves, and breaking internal waves. DAS amplitudes in the microseism band tracked sea-state dynamics during a storm cycle in the northern Pacific. These observations highlight this method’s potential for marine geophysics.
    Type of Medium: Online Resource
    ISSN: 0036-8075 , 1095-9203
    RVK:
    RVK:
    Language: English
    Publisher: American Association for the Advancement of Science (AAAS)
    Publication Date: 2019
    detail.hit.zdb_id: 128410-1
    detail.hit.zdb_id: 2066996-3
    detail.hit.zdb_id: 2060783-0
    SSG: 11
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
  • 6
    Online Resource
    Online Resource
    American Geophysical Union (AGU) ; 2017
    In:  Geophysical Research Letters Vol. 44, No. 23 ( 2017-12-16)
    In: Geophysical Research Letters, American Geophysical Union (AGU), Vol. 44, No. 23 ( 2017-12-16)
    Abstract: Distributed acoustic sensing (DAS) transforms fiber optics into dense seismic arrays (1 sensor/meter) using laser scattering Earthquake observations indicate that DAS and seismometer sensitivity is similar at 0.8‐1.6 Hz Fiber installed in telecommunication conduit shows sensitivity to propagating seismic waves
    Type of Medium: Online Resource
    ISSN: 0094-8276 , 1944-8007
    URL: Issue
    Language: English
    Publisher: American Geophysical Union (AGU)
    Publication Date: 2017
    detail.hit.zdb_id: 2021599-X
    detail.hit.zdb_id: 7403-2
    SSG: 16,13
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
  • 7
    Online Resource
    Online Resource
    Springer Science and Business Media LLC ; 2021
    In:  Scientific Reports Vol. 11, No. 1 ( 2021-03-10)
    In: Scientific Reports, Springer Science and Business Media LLC, Vol. 11, No. 1 ( 2021-03-10)
    Abstract: The sparsity of permanent seismic instrumentation in marine environments often limits the availability of subsea information on geohazards, including active fault systems, in both time and space. One sensing resource that provides observational access to the seafloor environment are existing networks of ocean bottom fiber optic cables; these cables, coupled to modern distributed acoustic sensing (DAS) systems, can provide dense arrays of broadband seismic observations capable of recording both seismic events and the ambient noise wavefield. Here, we report a marine DAS application which demonstrates the strength and limitation of this new technique on submarine structural characterization. Based on ambient noise DAS records on a 20 km section of a fiber optic cable offshore of Moss Landing, CA, in Monterey Bay, we extract Scholte waves from DAS ambient noise records using interferometry techniques and invert the resulting multimodal dispersion curves to recover a high resolution 2D shear-wave velocity image of the near seafloor sediments. We show for the first time that the migration of coherently scattered Scholte waves observed on DAS records can provide an approach for resolving sharp lateral contrasts in subsurface properties, particularly shallow faults and depositional features near the seafloor. Our results provide improved constraints on shallow submarine features in Monterey Bay, including fault zones and paleo-channel deposits, thus highlighting one of many possible geophysical uses of the marine cable network.
    Type of Medium: Online Resource
    ISSN: 2045-2322
    Language: English
    Publisher: Springer Science and Business Media LLC
    Publication Date: 2021
    detail.hit.zdb_id: 2615211-3
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
  • 8
    Online Resource
    Online Resource
    Frontiers Media SA ; 2020
    In:  Frontiers in Earth Science Vol. 8 ( 2020-6-16)
    In: Frontiers in Earth Science, Frontiers Media SA, Vol. 8 ( 2020-6-16)
    Type of Medium: Online Resource
    ISSN: 2296-6463
    Language: Unknown
    Publisher: Frontiers Media SA
    Publication Date: 2020
    detail.hit.zdb_id: 2741235-0
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
  • 9
    Online Resource
    Online Resource
    Oxford University Press (OUP) ; 2021
    In:  Geophysical Journal International Vol. 226, No. 1 ( 2021-04-12), p. 256-269
    In: Geophysical Journal International, Oxford University Press (OUP), Vol. 226, No. 1 ( 2021-04-12), p. 256-269
    Abstract: Surface wave retrieval from ambient noise records using seismic interferometry techniques has been widely used for multiscale shear wave velocity (Vs) imaging. One key step during Vs imaging is the generation of dispersion spectra and the extraction of a reliable dispersion curve from the retrieved surface waves. However, the sparse array geometry usually affects the ability for high-frequency ( & gt;1 Hz) seismic signals’ acquisition. Dispersion measurements are degraded by array response due to sparse sampling and often present smeared dispersion spectra with sidelobe artefacts. Previous studies usually focus on interferograms’ domain (e.g. cross-correlation function) and attempt to enhance coherent signals before dispersion measurement. We propose an alternative technique to explicitly deblur dispersion spectra through use of a phase-weighted slant-stacking algorithm. Numerical examples demonstrate the strength of the proposed technique to attenuate array responses as well as incoherent noise. Three different field examples prove the flexibility and superiority of the proposed technique: the first data set consists of ambient noise records acquired using a nodal seismometer array; the second data set utilizes distributed acoustic sensing (DAS) and a marine fibre-optic cable to acquire a similar ambient noise data set; the last data set is a vibrator-based active-source surface wave data. The enhanced dispersion measurements provide cleaner and higher-resolution spectra without distortions which will assist both human interpreters as well as ML algorithms in efficiently picking curves for subsequent Vs inversion.
    Type of Medium: Online Resource
    ISSN: 0956-540X , 1365-246X
    Language: English
    Publisher: Oxford University Press (OUP)
    Publication Date: 2021
    detail.hit.zdb_id: 3042-9
    detail.hit.zdb_id: 2006420-2
    detail.hit.zdb_id: 1002799-3
    SSG: 16,13
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
  • 10
    Online Resource
    Online Resource
    Oxford University Press (OUP) ; 2022
    In:  Geophysical Journal International Vol. 233, No. 1 ( 2022-11-29), p. 680-699
    In: Geophysical Journal International, Oxford University Press (OUP), Vol. 233, No. 1 ( 2022-11-29), p. 680-699
    Abstract: Passive seismic methods in highly populated urban areas have gained much attention from the geophysics and civil engineering communities. Linear arrays are usually deployed for passive surface wave investigations because of their high convenience, and passive surface wave imaging methods commonly used for linear arrays can be grouped as non-interferometric methods (e.g. passive multichannel analysis of surface wave, refraction microtremor) and interferometric methods (e.g. multichannel analysis of passive surface waves and spatial autocorrelation). It is well known that the seismic interferometry method is able to retrieve Green’s function between inter-station pairs based on passive seismic data and that is how interferometric methods work. Although non-interferometric methods are also popular and effective in near-surface seismic imaging, particularly in the geotechnical industry, there is no theoretical proof to clarify the accuracy and/or the bias of these methods. In this study, we use numerical derivations and simulations to demonstrate the underlying physics for both non-interferometric and interferometric methods, under two common noise source environments including a homogeneous source distribution and a dominant in-line source distribution. We also prove the strength of interferometric methods for accurate dispersion imaging over the non-interferometric methods, and provide a way to estimate the biases in non-interferometric measurements. Finally, we present comprehensive comparisons between different passive surface wave methods with three typical field examples considering various observation systems.
    Type of Medium: Online Resource
    ISSN: 0956-540X , 1365-246X
    Language: English
    Publisher: Oxford University Press (OUP)
    Publication Date: 2022
    detail.hit.zdb_id: 3042-9
    detail.hit.zdb_id: 2006420-2
    detail.hit.zdb_id: 1002799-3
    SSG: 16,13
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...